Technetium-99m (“Tc-99m”) is the most commonly used radioisotope in nuclear medicine. Tc-99m is used in approximately two-thirds of all imaging procedures performed in the United States. Tens of millions of diagnostic procedures using Tc-99m are undertaken annually. Tc-99m is a daughter isotope produced from the radioactive decay of molybdenum-99 (“Mo-99”). Mo-99 decays to Tc-99m with a half life of 66 hours.
The vast majority of Mo-99 used in nuclear medicine in the U.S. is produced in aging foreign reactors. Many of these reactors still use solid highly enriched uranium (“HEU”) targets to produce the Mo-99. HEU has a concentration of uranium-235 (“U-235”) of greater than 20%. Maintenance and repair shutdowns of these reactors have disrupted the supply of Mo-99 to the U.S. and to most of the rest of the world. The relatively short half-life of the parent radioisotope Mo-99 prohibits the build-up of reserves. One of the major producers, The National Research Reactor in Canada, will cease production in 2016.
An alternative strategy for providing Mo-99 is based upon the use of low enriched uranium (LEU), which presents a much lower nuclear proliferation risk than HEU. LEU has a concentration of U-235 of less than 20%, and many international Mo-99 producers are converting from HEU to LEU solid targets for Mo-99 production.
Several of the technologies currently being considered for the domestic supply of Mo-99 are based on the fission of U-235 in LEU. In all processes being considered, only a small fraction of the U-235 present in the irradiated target will be consumed during irradiation. Fission of U-235 generates a variety of fission products, one of which is Mo-99.
Some form of enriched uranium (HEU and/or LEU) is used for the production of Mo-99. After the fission process, the remaining uranium is typically discarded along with other fission products as waste. Recovery and purification of the uranium would make it available for reuse, storage, or disposal.
Therefore, an object of the present invention is to provide a process for recovering, and purifying, uranium from an irradiated solid target after separating Mo-99 produced from the irradiated target.